1. Field of the Invention
The present invention relates to a printing apparatus and a printing method, and relates in particular to a printing apparatus for high-speed paper supply and a printing method therefor.
2. Related Background Art
In a conventional apparatus, in order to increase printing speeds and to simplify mechanisms, a paper feeding mechanism, a paper conveying mechanism and a carriage mechanism are independently driven, or special motors are provided to drive these mechanisms at optimal timings.
However, the following problem plagues a conventional system, comprising these mechanisms, that initiates the feeding of a succeding printing medium without detecting the trailing end of a preceding printing medium. For example, when the lengths of printing media differ between a predecessor and a successor or when the lengths of the printing media vary, or when slippage occurs at a paper feeding mechanism, preceding and succeding media overlap each other, so that in a printing apparatus that has only one paper sensor a trailing edge of the preceding printing medium and a leading edge of the succeeding one cannot be discriminated, thereby causing paper feeding failures.
If the trailing end of the preceding printing medium is detected first and then the feeding of the succeeding printing medium is started, the above problem can be avoided. However, unless the sensor for the printing medium is located very near the feeding mechanism, a satisfactory effect can not be obtained because the interval between the preceding and succeeding printing media will be extended. Further, in the printing apparatus, the leading edges of printing media are detected immediately after the media are fed by a feeding mechanism, so that, if because of slippage the feeding distance of the printing media varies before they reach the sub-scanning mechanism, there is no means available to correct such variation. Therefore, no conventional printing apparatuses can cope with reductions in the intervals between printing media that are consecutively fed, stabilization in positioning the leading edges, and differences in the lengths of printing media. For removing the above-mentioned trouble, it is generally effective to employ two paper sensors, but such a use results in increased manufacturing costs.